It is possible to couple a gas turbine engine to a pump and thereby supply power to the pump to pump fluid. However, gas turbine engines typically operate at much higher rotational speeds than pumps. For example, some gas turbine engines may operate efficiently at about 15,000-16,000 revolutions per minute (rpm), while some pumps may operate at speeds of up to about 2,000 rpm. It is possible to couple the gas turbine engine to a pump via a reduction gear assembly, so that the operating speed of the gas turbine engine is compatible with the operating speed of the pump.
However, in some applications it may be desirable to operate a pump at varying speeds based on conditions of the fluid being pumped. For example, it may be desirable to operate at a speed much lower than the normal operating speed of the pump. In such situations, a gas turbine engine may be unsuitable for supplying power to the pump because it may operate efficiently in only a relatively narrow range of operating speeds compared to the pump.
A system employing a torque converter and a synchronizing motor to start up a large rotational driver/load combination is disclosed in U.S. Pat. No. 7,422,543 B2 to Ransbarger et al. (“the '543 patent”). In particular, the '543 patent discloses a torque converter employed to increase the rotational speed of a load to a maximum speed permitted by the torque converter. The synchronizing motor is then employed to further increase the rotational speed of the load to substantially match the rotational speed of the driver.
Although the '543 patent discloses use of a torque converter to couple a gas turbine engine to a load, the system disclosed in the '543 patent may suffer from a number of potential drawbacks due to, for example, insufficient control of the output of the torque converter. Thus, it may be desirable to mitigate or overcome these potential drawbacks to improve control of the output of the torque converter.